I'm assuming that you don't have these chicks with a hen?
I would put them in a cage at first, so the bigger hens can't hurt them, for a while, to let the others get used to them.
Do the others free range, or are they in a coop? If they are in a coop, put the young chicks cage inside the coop. If they free range, put the cage where the others hang out the most, out of the sun of course.
But you definitely need to keep the babies safe, I would say for a few weeks at least. It would be good to have someplace for the babies to hide, where the others can't get to them, like a box or something they can get under.
Just be sure to watch them once you do let them run together, to make sure the bigger hens aren't bullying too badly.
<edited for better organization!
was kind of rambly!!)